The attorney general, Eric Holder, has indicated that the US could allow the national security whistleblower Edward Snowden to return from Russia under negotiated terms, saying he was prepared to “engage in conversation” with him.

Holder said in an MSNBC interview that full clemency would be “going too far”, but his comments suggest that US authorities are prepared to discuss a possible plea bargain with Snowden, who is living in exile in Russia.

Snowden, who took part in a live webchat at about the same time Holder’s remarks were made public, defended his leaks, saying weak whistleblower protection laws prevented him from raising his concerns through formal channels.

“If we had ... a real process in place, and reports of wrongdoing could be taken to real, independent arbiters rather than captured officials, I might not have had to sacrifice so much to do what at this point even the president seems to agree needed to be done,” Snowden said.

He gave no indication in the live chat whether he would consider any plea bargain or negotiated return to the US. Asked under what conditions he would return to his native country, Snowden replied: "Returning to the US, I think, is the best resolution for the government, the public, and myself, but it’s unfortunately not possible in the face of current whistleblower protection laws, which through a failure in law did not cover national security contractors like myself."

The Obama administration’s official line is that Snowden is a suspected felon and should be extradited from Russia, where he has been granted temporary asylum, to face trial in the US. Snowden has yet to be publicly indicted by the Justice Department, but in June it charged him with violations of the Espionage Act.

But Holder is the third senior administration official, including the president, who has made comments that raise the question of Snowden returning to the US under some kind of negotiated terms.

Jay Carney, the White House spokesman, was repeatedly pressed on Thursday over whether the administration “ruled out” clemency for the whistleblower. “He has been charged with felonies,” Carney replied. “I am not going to wade into those kind of assessments.”

MSNBC only released short excerpts of its interview with Holder, but reported the attorney general said he “would engage in conversation” with Snowden if he accepted responsibility for leaking government secrets.

Holder also said full clemency “would be going too far”, according to the network. Asked whether Snowden was a whistleblower, he replied: “I prefer the term defendant. That’s the most apt title.”

The network said Holder made similar remarks at the University of Virginia, quoting him as saying: “We've always indicated that the notion of clemency isn't something that we were willing to consider. Instead, were he coming back to the US to enter a plea, we would engage with his lawyers. ”

Snowden has never denied leaking the documents, but insisted his decision to provide top-secret documents to reporters working for the Guardian and Washington Post was an act of conscience, designed to inform the public about the nature of NSA surveillance.

In the webchat, Snowden said he did not believe he would receive a fair trial in the US. "The 100-year-old law under which I’ve been charged, which was never intended to be used against people working in the public interest, and forbids a public interest defence," he said. "This is especially frustrating, because it means there’s no chance to have a fair trial, and no way I can come home and make my case to a jury."

Snowden’s critics have argued that he is not a legitimate whistleblower because he did not take his concerns to intelligence inspectors general or members of Congress on the intelligence oversight committees.

A former NSA contractor with Booz Allen Hamilton, Snowden defended his leaks in the live chat, pointing out that intelligence-community contractors are not covered by whistleblower protection laws.

“There are so many holes in the laws, the protections they afford are so weak, and the processes for reporting they provide are so ineffective that they appear to be intended to discourage reporting of even the clearest wrongdoing,” he said.

“If I had revealed what I knew about these unconstitutional but classified programs to Congress, they could have charged me with a felony.”

The whistleblower’s supporters argue out that he would unable to mount a proper defence in a US courtroom, in part because he would be barred from discussing the classified government programs.

A judge would also be likely to instruct the jury that Snowden’s intentions would not constitute a defence of the charges against him. Some scholars have said Holder should adapt the rules to recognise the unique nature of the case.

“The Department of Justice and Snowden’s attorneys could agree to conduct it by a slightly different set of rules, rules that would permit the jury to consider the full extent of the alleged governmental wrongdoing he uncovered along with the full scope of his alleged crimes,” Alex Little, a former CIA analyst and assistant US attorney, wrote recently.

Holder’s remarks are the latest in a series of hints the administration might consider some kind of plea bargain with the former contractor. Such a move that would be deeply unpopular with intelligence officials and their supporters on Capitol Hill.

In remarks published six days ago, Obama appeared to leave the door open to some kind of arrangement with Snowden.

A 17,000-word New Yorker profile of the the president, written by the magazine’s editor, David Remnick, quoted him as saying Snowden was “not akin to Watergate or some scandal in which there were coverups involved”. He also insisted “the benefit of the debate he generated was not worth the damage done, because there was another way of doing it”.

However, in remarks to Remnick the day before he gave last week's long-awaited speech on the NSA, Obama said: “I do not have a yes/no answer on clemency for Edward Snowden. This is an active case, where charges have been brought.”

Last month, Richard Ledgett, the NSA official in charge of assessing the alleged damage caused by Snowden’s leaks, raised the possibility of an amnesty in return for assurances that top-secret material could be secured.

“My personal view is, yes, it’s worth having a conversation about,” he told CBS News. “I would need assurances that the remainder of the data could be secured, and my bar for those assurances would be very high. It would be more than just an assertion on his part.”

In Thursday’s webchat, Snowden also said a report by the government’s independent civil liberties watchdog, the Privacy and Civil Liberties Oversight Board, vindicated his actions. The divided board found that the bulk collection of Americans’ phone data was illegal and ought to end.

“There is simply no justification for continuing an unconstitutional policy with a 0% success rate,” Snowden said.